Expulsion of cadmium from a simulated wastewater using CKD as adsorbent: Optimization with isotherm study

Cement kiln dust (CKD) considers as an inexpensive, abundant adsorbent and was used in the present work for removing cadmium ions from a simulated wastewater. CKD was obtained from Al-Duh Cement Factory located in south of Al-Muthanna Governorate/Iraq and identified by X-ray diffractometer (XRD), scanning electron microscopy (SEM) with EDX, and Fourier transform infrared spectrometry (FTIR). Optimization of the main effective parameters like initial cadmium concentration, CKD dosage, shaking speed, pH and contact time on the cadmium removal efficiency was achieved via applying reaction surface strategy (RSM). Results showed that underlying cadmium fixation has the fundamental impact on the cadmium removal efficiency followed by CKD dosage, time, pH, and lastly shaking speed. The preferred operating conditions were found to be an initial Cd concentration of 20 ppm, CKD dosage of 35 g \ L, pH of 8, shaking speed of 300 rpm, and contact time of 90 minutes. Based on these optimum conditions, 99.75% removal efficiency of cadmium was obtained. The adsorption isotherm results showed that the adsorption behavior of Cd ions on CKD agree well with Langmuir model. CKD seems to be a systematic, sustainable and economic material for cadmium removal from wastewater.